At the present time, extending the processing capacities of vibratory equipment under development is an urgent problem since it allows reductions in the component machining time and, consequently, in power consumption, which leads to increased productivity per unit time and improved quality of vibration treatment. Unbalance vibrator used most commonly for the generation of disturbing forces are of the mechanical inertia unbalance type which offers simplicity in operation and fairly high disturbing forces. Under operation conditions, a necessity may often arise for the amount of disturbing force generated by the vibratory device to be adjusted over a wide range, for example, in order to adjust the oscillation amplitude in the vibratory device.
The amount of vibrational force generated is directly proportional to the mass of unbalance weight, which is arranged eccentrically with respect to the axis of rotation of the drive shaft, the distance of the center of this mass from the axis of rotation of the drive shaft, and to the squared frequency of rotation (angular velocity) of the drive shaft.
By virtue of the fact that varying the frequency of rotation of the drive shaft over a wide range necessitates the use of a d.c. motor in conjunction with a supply voltage regulator, the simplest ways of varying the amount of the disturbing force would be either by changing the eccentric mass of the unbalance vibrator or by altering the distance from the center of its masses to the axis of rotation of the drive shaft.
Known in the present state of the art in unbalance vibrator (SU, A, 956,051) comprising a drive shaft, two unbalance weights, which are mounted on the drive shaft so as to be turnable with respect to each other, a mechanism for adjusting the mutual position of the unbalance weights, which is made in the form of a rod and a hollow cylinder having helical grooves provided on its cylindrical surface, each of the grooves being adapted to interact with one of the unbalance weights. The cylinder is installed so as to be traversable lengthwise the shaft, and the rod is connected to the cylinder. A disadvantage inherent in the device described above resides in the fact that the mechanism for adjusting the mutual position of unbalance weights is too cumbersome and features sophisticated construction.
The closest to the herein proposed invention is a centrifugal unbalance vibrator (DE, C, 1,297,928) comprising a fixed a shaft fitted in a rotary electric motor. Fixed stationary on the housing of the electric motor is an unbalance weight made in the form of an arc-shaped guideway supporting another movable unbalance weight made in the form of an arc-shaped element. The unbalance weights are provided with a mechanism for adjusting their mutual position and fashioned as a pin retainer spring-loaded in a radial direction. One end of the retainer engages in one of the radial through holes provided in the movable weight so that movement of the movable unbalance weight will cause a change in the amount of the disturbing force produced by the unbalance vibrator.
A substantial disadvantage of the prior-art unbalance vibrator mentioned above resides in the fact that the mechanism for adjusting the mutual position of the unbalance weights does not allow the disturbing force to be varied over a wide range, or its smooth adjustment, which prevents vibration treatment of a wide range of products. Inconvenience caused by the prior-art unbalance vibrator lies with the sophisticated adjustment of the disturbing force, since the adjustment process involves the use of an additional tool, such as a cylindrical pin or rod, which has to be fitted, in succession, in each of the through holes passing underneath the extensible retainer, thus increasing the total adjustment time.
Furthermore, the unbalance vibrator discussed above features a comparatively high drag coefficient because of the clearance between the movable unbalance weight and the motor housing, which increases noise when the unbalance vibrator operates.